Optical Properties Of Quantum Emitters In Hexagonal Boron Nitride In Cryogenic Thermal Shock

Mai, Thi Ngoc Anh

Optical Properties Of Quantum Emitters In Hexagonal Boron Nitride In Cryogenic Thermal Shock

Mai, Thi Ngoc Anh

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Publication Type:: Thesis
Issue Date:: 2025

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Field	Value	Language
dc.contributor.author	Mai, Thi Ngoc Anh
dc.date.accessioned	2025-11-04T00:25:02Z
dc.date.available	2025-11-04T00:25:02Z
dc.date.issued	2025
dc.identifier.uri	http://hdl.handle.net/10453/190605
dc.description	University of Technology Sydney. Faculty of Engineering and Information Technology.	en_US.UTF-8
dc.description.abstract	Quantum information science promises to usher in a new era of analyzing, processing, and transferring information in manners unimaginable decades ago. At the heart of these protocols is quantum hardware known as quantum emitters—molecular-sized entities emitting a single photon at a time. Compared to their gas-phase counterparts, quantum emitters in solids have gained tremendous traction owing to their unique suite of properties, such as room-temperature operation, high photostability, and ease of usage. One of the front-runners in this category is quantum emitters in hexagonal boron nitride (hBN) since they offer incredibly high brightness, high single-photon purity, chemical inertness, and low fabrication cost. The quantum emitters have been, therefore, recently considered for space-related communication applications such as satellite-ground quantum key distribution. To enable this task, the quantum emitters must be tested against thermal shocks—similar to those encountered in space. Such a study has, however, remained elusive to date. This thesis presented a statistical test on hBN quantum emitters under different temperature drop protocols. The optical properties including photoluminescence spectra, zero phonon line peak, full width at half maximum, photostability, single-photon emission rate and lifetime, of quantum emitters in hBN flakes are studied in detail. By using a combination of different structural characterizations such as atomic force microscopy, transmission electron microscopy, X-ray diffraction, and density functional calculations, it was confirmed that the observed spectral shifts and photo-bleaching of hBN quantum emitters are attributed to lattice strain caused by cryogenic temperature shock. Furthermore, a slow-cooling process is shown to alleviate such detrimental changes. This work provides insights into the stability of the quantum emitters under harsh conditions resembling those faced in outer space. It also proposes a more thorough testing method for quantum emitters in future space-based quantum applications.	en_US.UTF-8
dc.format	Thesis (PhD)
dc.language.iso	en_US	en_US.UTF-8
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/190605/1/thesis.pdf
dc.rights	info:eu-repo/semantics/openAccess
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	© 2025 Thi Ngoc Anh Mai
dc.rights	au.edu.uts.lib/cph
dc.title	Optical Properties Of Quantum Emitters In Hexagonal Boron Nitride In Cryogenic Thermal Shock	en_US.UTF-8
dc.type	Thesis
utslib.copyright.status	open_access	*

Abstract:

Quantum information science promises to usher in a new era of analyzing, processing, and transferring information in manners unimaginable decades ago. At the heart of these protocols is quantum hardware known as quantum emitters—molecular-sized entities emitting a single photon at a time. Compared to their gas-phase counterparts, quantum emitters in solids have gained tremendous traction owing to their unique suite of properties, such as room-temperature operation, high photostability, and ease of usage. One of the front-runners in this category is quantum emitters in hexagonal boron nitride (hBN) since they offer incredibly high brightness, high single-photon purity, chemical inertness, and low fabrication cost. The quantum emitters have been, therefore, recently considered for space-related communication applications such as satellite-ground quantum key distribution. To enable this task, the quantum emitters must be tested against thermal shocks—similar to those encountered in space. Such a study has, however, remained elusive to date. This thesis presented a statistical test on hBN quantum emitters under different temperature drop protocols. The optical properties including photoluminescence spectra, zero phonon line peak, full width at half maximum, photostability, single-photon emission rate and lifetime, of quantum emitters in hBN flakes are studied in detail. By using a combination of different structural characterizations such as atomic force microscopy, transmission electron microscopy, X-ray diffraction, and density functional calculations, it was confirmed that the observed spectral shifts and photo-bleaching of hBN quantum emitters are attributed to lattice strain caused by cryogenic temperature shock. Furthermore, a slow-cooling process is shown to alleviate such detrimental changes. This work provides insights into the stability of the quantum emitters under harsh conditions resembling those faced in outer space. It also proposes a more thorough testing method for quantum emitters in future space-based quantum applications.

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http://hdl.handle.net/10453/190605